A vehicle includes a number of devices that use heat produced by an internal combustion engine, such as a heater device or an oil warmer. However, as engines have become more efficient and more compact to improve combustion performance, engine heat has decreased, thus making it difficult to ensure production of a sufficient quantity of heat. To solve the problem, there is a demand for heat use efficiency to be improved.
Conventionally, a control device described in Patent Document 1 has been proposed as a control device intended to ensure production of a necessary quantity of heat for a heater device for a vehicle having a low-displacement and low-heat-generation internal combustion engine. The control device described in Patent Document 1 carries out heat generation increase control by raising the engine idle speed and retarding the ignition timing when various conditions are met, or, specifically, on condition that the engine is in idle operation, that the heater device is in operation, that the engine coolant temperature is less than a set value, and that the increase rate of the engine coolant temperature is less than a set value.
The conventional control device for a vehicle increases the quantity of heat produced by the engine by raising the engine idle speed and retarding the ignition timing when it is determined that the engine coolant temperature is low and increases only with a small increase rate and thus the quantity of heat supplied to the heater device will likely fall short. As a result, in using the control device, heating performance of the heater device is prevented from being lowered to a certain extent.